This invention relates to devices for interconnecting circuit devices such as IC packages to circuit boards, circuit boards and modules to circuit boards or substrates, and substrates to substrates. Specifically, the invention relates to low impedance surface-mount connectors. In addition to having advantageous qualities of compactness, low interconnection resistance, low inductance, and mechanical compliance, the connectors permit easier inspection of the solder bonds between the circuit devices.
As electronic circuits become denser, faster and increasingly complex, devices for interconnecting them are subject to more demanding requirements. With the great increase in the density of active components, interconnection devices become large consumers of available volume. And increased density brings an increase in required currents and power dissipation, aggravating thermal mismatch between connected circuit devices. In addition, higher circuit device speeds place stricter constraints on tolerable interconnect inductance.
U.S. patent application Ser. No. 09/737,303 describes a low impedance surface-mount connector comprising a length of cylindrical rod having an I-shaped cross section. The device permits interconnection by pick-and-place techniques. A first circuit device having one or more circuit components is interconnected with a second circuit device by surface mounting such connectors on the first circuit device, providing corresponding solder pads on the second circuit device, and mounting the connectors of the first circuit device onto the pads of the second.
This interconnection has advantageous qualities of low resistance, low inductance, mechanical compliance and ease of manufacture. However, it does not permit vertical visual inspection of the solder bonds at the point of connection of the first circuit device to the second. One looking down from above cannot see the solder connection between the connector and the solder pad on the second device. Accordingly there is a need for interconnection devices that can be inspected more easily.
In accordance with the invention, an I-channel surface mount connector comprising a length of cylindrical rod having a generally I-shaped cross section is improved by providing an extended mounting flange. When a first circuit device is connected to a second circuit device with the extended flange extending outward of the first device, the flange can extend beyond the periphery of the first device. This extension has the advantage that the solder bond between the flange and the second device can be easily inspected from above using visual inspection equipment.